One of the most common patterns with command line programs is the need to print lists of data. cliff provides a base class for commands of this type so that they only need to prepare the data, and the user can choose from one of several output formatter plugins to see the list of data in their preferred format.
The cliff.lister.Lister base class API extends Command to allow take_action() to return data to be formatted using a user-selectable formatter. Subclasses should provide a take_action() implementation that returns a two member tuple containing a tuple with the names of the columns in the dataset and an iterable that will yield the data to be output. See the description of the files command in the demoapp for details.
cliff is delivered with two output formatters for list commands. Lister adds a command line switch to let the user specify the formatter they want, so you don’t have to do any extra work in your application.
The csv formatter produces a comma-separated-values document as output. CSV data can be imported into a database or spreadsheet for further manipulation.
(.venv)$ cliffdemo files -f csv
"Name","Size"
"build",136
"cliffdemo.log",2690
"Makefile",5569
"source",408
The table formatter uses PrettyTable to produce output formatted for human consumption.
(.venv)$ cliffdemo files
+---------------+------+
| Name | Size |
+---------------+------+
| build | 136 |
| cliffdemo.log | 2546 |
| Makefile | 5569 |
| source | 408 |
+---------------+------+
Formatters using tablib to produce JSON, YAML, and HTML are available as part of cliff-tablib.
If the standard formatters do not meet your needs, you can bundle another formatter with your program by subclassing from cliff.formatters.base.ListFormatter and registering the plugin in the cliff.formatter.list namespace.